Biology Lab Report 10(Ecology)
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INTERNATIONAL EDUCATION CENTRE (INTEC) UNIVERSITI TEKNOLOGI MARA
MUHAMAD ALEIFF BIN TAJUDDIN
PATTERNS IN DISTRIBUTION AND ABUNDANCE OF ORGANISMS OF A HABITAT
MDM SIVARANI D/O RAJADURAI
Aim:To investigate the patterns of the distribution and abundance of various organisms at the sea shore.
Abstract:The aim of the experiment was to study the distribution and abundance of the species of organisms found at the sea shore. The distribution and the abundance of the species depend on the biotic and the abiotic factor which was present in the location. The results of this experiment show that the distribution of the sea grass has the greatest distribution and the most abundant species. The result had been achieved by using the quadrat sampling technique and the line transaction method.
Introduction:The word ecology comes from the Greek word ‘oikos’ meaning ‘house’. It is actually the study of the interactions that determines the distribution and abundance of organisms within a particular environment. Therefore, ecology is actually the study of living things in their home environment or habitat. In this experiment we are going to study the ecology at the sea shore. Sea shore is a unique area in which it is periodically
and exposed by the tides, twice
longer exposure to air and greater
temperature and salinity. Changes
Figure 1: The sea shore where the investigation had been carried out.
conditions from the upper to the lower intertidal zones limit the distributions of many organisms to particular strata. The oxygen and nutrient levels are generally high and renewed with each turn of the tides. Abiotic factors are the non-living elements of the habitat of an organism. They include those related to the climate, such as the amount of sunlight, temperature extremes and rainfall, and those soil-related including the drainage and the pH of the environment. In aquatic habitats the oxygen availability in the water is very important. Other than that, the salt content and the nutrients in the water also important to the organisms that live in aquatic habitat. Environmental temperature is also an important factor in the distribution of organisms because of its effect on biological processes. Cells may rupture if the water they contain freezes and the proteins of most organisms denature at temperatures above 45 . In addition, just a few organisms can maintain active metabolism at very low temperatures, through extraordinary adaptations enable some organisms, such as thermophilic prokaryotes, to live outside the temperature range habitable by other life. Most organisms function best within a specific range of environmental temperature. Temperature outside that range may force some animals to expand energy regulating their internal temperature, as mammals and birds do. The dramatic variation in water availability among habitat is another important factor in species distribution. Species living at the sea shore or in tidal wetlands can dehydrate or dry out as the tides recedes. The salt concentration of water in the environment affects the water balance of organisms through osmosis. Most aquatic organisms are restricted to either freshwater or salt water habitats by their limited ability to osmoregulate. The amount of light in a habitat has a direct impact on the numbers of organisms found there. Plants are dependent on light for photosynthesis. Any plant populations which are going to thrive in habitats with low light levels must be able to cope with this factor. Animals are affected by the light levels indirectly as a result of the distribution of the food plants. Seasonal light change can also affect the reproductive patterns and without the cues from changing light level , many aspects of animal behavior would be lost.
Biotic factors are the living elements of a habitat which affect the ability of a group of organisms to survive there. For example, the presence of a suitable prey species will affect the number of predators in the habitat. Other than that, finding a mate, territory, competition, parasitism and disease also the examples of biotic factor. A mathematical model that describes the relationships between predator and prey population predicts that the populations will oscillate in a repeating cycle. The reasoning underlying this model is straightforward. As a prey population increases there is more food for predators and so, after an interval, the predator population grows too. The predators will increase to the point where they are eating more prey than they are replaced by reproduction, so the numbers of prey will fall. This will reduce the food supply of the predators, so they will not produce as many offspring, and so their numbers will fall as well, allowing the abundance of prey to increase again and so on. Reproduction is a powerful driving force and the likelihood of finding a mate, or achieving pollination, will help to determine the organisms which are found in any habitat. So, if a single seed is dispersed to a new area, germinates, grows and survives, that species of plant is unlikely to become a permanent resident unless other plants of the same species live in the habitat. There must be males and females so mates can be found. Availability of mates has a big effect on the abundance of any type of animal in an area. Many species of animals show a very clear territorial behavior. A territory is an area held and defended by an animal or group of animals against other organisms which may be of the same or different
functions in different animals but they are almost always used in some way to make sure that a breeding pair has sufficient resources to raise young. The type and size of territory will help to
Figure 2: Penguin territory in the pole.
determine which species live in a particular community. Parasitism and disease are biotic factors which can have devastating effect on individuals. Diseased animals will be weakened and often do not reproduce successfully. Sick predators cannot hunt well, and diseased prey animals are more likely to be caught. Some diseases are very infectious and can be spread without direct contact such as avian flu which can be spread in the faeces of an infected bird. We have used quadrats to estimate the abundance of each species. A quadrat marks off an area of ground within which you can make a thorough survey of which species are present, and how many of each of them there are. If quadrat is too big, it is very difficult to do this accurately. If the quadrat is too small, it does not give you a very good sample of the habitat as a whole. Random sampling is usually carried out when the area under study is very large, or there is limited time available. When using random sampling techniques, large numbers of samples/records are taken from different positions within the area. A numbered grid should be overlaid over a map of the area. A computer generated random number table is then used to select which squares to sample in. For example, if we have mapped a representative zone, and have then laid a numbered grid over it as shown below, we could then choose which squares we should sample in by using the random number table. The advantage of using random numbers is that no human is involved in the selection process. Systematic sampling is when samples are taken at fixed intervals usually along a line. This normally involves doing transects, where a sampling line is set up across areas where there are clear changes. For example you might use a transect to show how gentrification or the price of a convenience item changes with increasing distance from a zone of inner city redevelopment. A transect line is laid across the area you wish to study. The position of the transect line is very important and it depends on the direction of the environmental gradient you wish to study. It should be thought about carefully before it is placed. You may otherwise end up without clear results because the line has been wrongly placed. For example, if the area of
redevelopment was wrongly identified in the example given above, it is likely that the transect line would be laid in the wrong area and the results would be very confusing. A line transect is carried out by drawing the transect line along the gradient identified. Alternatively, the presence, or absence of a particular service or feature at each marked point, (e.g. every 100 metres), may be recorded. This is called systematic sampling.
Problem statement:Does abiotic and biotic factor affect the distribution and abundance of organisms at the sea shore?
Hypothesis:The biotic and abiotic factors affect the distribution and abundance of organisms at the sea shore.
Variables:a) Manipulated variable
Distance of quadrat from the shore.
b) Responding variable
Population distribution and abundance of organisms.
c) Fixed variable
Current velocity, Seawater pH, seawater content of iron, nitrite, nitrate, phosphate, total chloride, free chloride and magnesium hardness.
An orange pH indicator Nitrite indicator Chloride indicator Magnesium indicator Nitrate indicator Phosphate indicator Iron indicator
Sticks Measuring tape Quadrat Stopwatch Small quadrat
Table 1: Materials and apparatus
Procedure:a) Estimating population size. 1. Line transect method was used to estimate the population size of organisms on the rocky shore. 2. A suitable place was chosen as the area of investigation. 3. A measuring tape was laid from the sublittoral zone to eulittoral to splash zone. 4. Two sticks were used to mark the starting and
Figure 3: Line transect that had been used in this experiment
the ending point. 5. Next, a quadrat was placed at the right of the line transect at four random places. 6. The
determined and the number of the species in the quadrat was calculated. For small organisms, a small quadrat was placed inside the large quadrat. 7. The data obtained were recorded in the table.
Figure 4: Quadrat and small quadrat
b) Determine current velocity 1. A suitable straight stretch of water has been chosen. The distance was measured with the tape measure. 2. The time taken by an orange to travel along the measured distance was recorded by using stopwatch. 3. Step 2 was repeated three times to obtain the mean. 4. Then, the mean time was divided by the coefficient 0.85. This gave a more accurate velocity for the stream because the water at the surface flows faster than the beneath. 5. The velocity was calculated using the formula: Velocity = distance
c) Investigate the pH of water sample, the free chloride/total chloride, the nitrite content, magnesium hardness, phosphate content, iron content, and nitrate content. 1. A water sample was taken from an area of investigation. 2. The water sample was put into a clean beaker. 3. The pH of the water sample was test by using pH indicator by dipping it into the water sample. 4. The colour change of the pH indicator was observed and compared with the standard pH indicator. 5. Next, the paper indicator was dip into the water sample to test the total and free chloride, nitrite content, nitrate content, phosphate content, iron content and magnesium hardness. 6. Steps 1 until 5 were repeated with the water sample from different places from the same area of investigation.
Results:a) Profile diagram.
Figure 5: Profile diagram of the sea shore.
Position on line transect
0.0m – 2.0m
2.0m – 8.0m
Rock & Water on the surface
8.0m – 15.6m
15.6m – 23.52m
Mostly flat rocks
Table 2: Description of the profile diagram
b) Quadrat sampling.
Position on transect line 17.61m - 18.12m
Organisms found Sea grass
No. of organnisms 95000
Note On the rock surface
15.15m - 15.65m
10.64m - 11.15m
5.76m - 6.27m
Half rock and
half sea water
In the sea
Table 3: Type and abundance of organisms which have been found in the quadrat sampling.
The ACFOR scale for the population size of species along the line transect
999 ~ 800
99 ~ 80
799 ~ 600
79 ~ 60
599 ~ 400
59 ~ 40
39999 ~ 0
399 ~ 0
39 ~ 0
Table 4: ACFOR scale The results from the 4 quadrats used
A (furthest from
Species found in the quadrat
Population size of each species in the quadrat (x 2500cm² if using 1cm² quadrat) 38 x 2500= 95000
Number of species found within the quadrat 1
5.5 x 2500= 13750
the beach) B
4 Sea cucumber
4 x 2500= 10000
D (closest to the
Sea grass Fish
34 x 2500=85000 1
Table 5: ACFOR scale according to each species of organisms in each quadrat
Kite diagram. 5
0 Quadrat A(furthest from the beach)
0 Quadrat A -5
Figure 6: Kite diagrams showing frequency and distribution of 6 species of organisms found at the sea shore.
c) Test for Water Sample Water pH sample 1
Total iron content
Total phosphate content 15
Magnesium hardness 25 gpg
Total nitrate content 0
Total nitrite content 0
Table 6: Result for Water Samples’ Test
d) Current velocity i)
Taverage = =
Total - 0 Free - 0
Total - 0 Free - 0
Total - 0 Free - 0
Discussion:Analysis of data: Figure 6 shows the profile diagram of the sea shore from the sublittoral zone to eulittoral to splash zone. Area labelled (a) is totally immersed in the sea water. Area labelled (b) is a large rock with a small part of sea water on it. Mostly sea water at the area labelled with (c) and mostly flat rocky surface covered the area labelled (d). Quadrat 1(QA) is in the (d) area which is on the flat rocky surface. Quadrat 2(QB) and quadrat 3(QC) were in the (c) area in which QB was at the area consisted of half sea water and half rocky surface. The last quadrat which is on the surface of the large rock was quadrat 4(QD). Table 2 shows the description of the profile diagram of the sea shore. The table gave us the information about the position of each area on the line transection. Area (a) was from 0.0m to the 2.0m away from the sea while the area (b) was from 2.0m to the 8.0m, followed by area (c) from 8.0m to the 15.6m distance away from the sea. The last area which was (d) located at the 15.6m to 23.52m away from the sea. Table 3 gives us the information about the species and the abundance inside the quadrat. For the QA, it was placed at the 17.61m to 18.12m on the line transect. The species that we found there was only sea grass on the rock surface. In the case of quadrat QB, it was situated at the 15.15m to 15.65m on the line transect. The species that we found in the quadrat was barnacles X and Y, sea cucumber and crab. We found the barnacle X and Y on the rock surface while the crab and the sea cucumber were in the water. The third quadrat which is Q C was placed at the 10.64m – 11.15m. The species that we found here was barnacle X and Y again and sea cucumber as well. The last quadrat consists of sea grass, barnacle Z and W and small fish. The quadrat was situated at the 5.76m – 6.27m. We found all of these species on the large rock that had water at its surface. Table 4 shows the ACFOR scale that we used to make a kite diagram. Table 5, was the table that I used to make reference to complete the kite diagram. Figure 7 was the kite diagram that we obtained from this experiment. We can see the pattern for each species. For barnacles X, we can see that the species was large in number in quadrat B and C. Same pattern was shown by
the barnacles Y and sea cucumber. Crab was only found in quadrat B while fish was only found in the quadrat D. Lastly, the sea grass was large in number in the Quadrat A and Quadrat B. It is clearly depicted that the most related abiotic factors for the species that live in the ecosystem are the exposure towards the sunlight, humidity, water salinity and the water current during low tide. In quadrat A and D, most of the sea grass grows on the surface of the rock to obtain optimum exposure towards the sunlight. Meanwhile, in quadrat B and C, the growth of the barnacles species mostly seen at the side of the rock which indicates us about the relative humidity and the little exposure of the sunlight on them. This case also tells us about the durability of the barnacles’ species towards the water current. The discovery of the sea cucumber in quadrat B and C along the line transect at the seashore shows us that the species can live in water with high salinity. Another reason why the distribution of organisms was found to be like this lies in the level of H+ ions and OH- ions of seawater. Lower H+ ions will indicate that the seawater is acidic while higher OH- ions content will resulted in alkaline seawater. Most marine and aquatic organisms can only live in neither acidic nor alkaline condition. Based on the results above, we can see the relationship between the level of pH value of seawater with the abundance and distribution of marine species. The phosphate content of seawater dropped from 15 ppm in water sample A into only 5 ppm in water sample 2 and 3. Around the area in which water sample 1 was taken, the abundance of sea grass found was very high (with 15 ppm of phosphate) while there was no other species of organisms found in that particular area. Meanwhile, around the area in which water sample B and C was taken (with 5 ppm of phosphate), the abundance and distribution of seed grass was completely zero whereas the number of other marine organisms increases. This phenomenon is best explain with the fact that higher concentration content of phosphate in seawater may resulted in the destruction in the sensible biological balance of marine habitats. Higher phosphate content is the most favourable condition for seed grass, blue and green algae to live and reproduce rapidly while for other marine organisms it is vice versa. This is because large number of algae (due to the high phosphate content) may grow on the body of other marine organisms and eventually kill them. Even the algae found on corals called zooxanthella will grow very fast and the corals will
be badly affected. Based on the findings in the internet, the suitable condition for the growth of marine organisms will be between 5 to 20 ppm. Table 6 above shows the pH value and chemical content of seawater found at the experiment site. From the result we can see the water sample 1 that was taken in front of a rock contain 0 ppm of iron, nitrite, nitrate, total and free chloride. The pH value was 8 and it is a sign that seawater sample taken from that place was slightly alkaline. Its magnesium hardness was found to be 425 ppm and 15 ppm of phosphate content. For water sample 2 which was taken behind a rock, it has a pH value of 7 which is neutral. Despite its neutrality, that particular water sample still has the same magnesium hardness which was 425 ppm and 0 ppm of iron, nitrite, nitrate, total and free chloride content. However, its phosphate content was found to be different with water sample A that is 5 ppm. As for water sample 3, it was taken near the quadrat 1 location and it still has 425 ppm of magnesium hardness, pH value of 7, phosphate content of 5 ppm and iron, nitrite, nitrate, total and free chloride content of 0 ppm. The (d) shows the calculation involving in determining current velocity. A distance of 2m was measured and an orange was used as the float thing. 3 trials were done in order to obtain the average value of the time taken for the orange to travel 2m distance on the seawater. The time taken was 52.6 s, 64.0 s and 73.0 s for trial 1, 2 and 3 respectively. The average time taken was found out to be 63.2 s. The average time taken was then divided by 0.85 to give a more accurate velocity for the stream because water at the surface flows faster than that beneath and the new average time taken was 74.4 s. For the calculation of current velocity, the distance of 2 m was then divided by 74.4 s. The current velocity was found to be 0.02688 ms-1.
Validity and reliability: It is vivid that the validity of the experiment conducted above is satisfying enough. This is because in the experiment, there were 2nd time and 3rd time in taking the reading of the time taken for the orange to complete the 2m journey on seawater freely so that average reading can be taken. As for the number of organisms found, although the counting process was actually been done once but it is highly accurate because more than one person involved in the counting process. Therefore we can say the result obtained is valid. Furthermore, the reliability of this experiment is said to be correct and reliable. This is because the results obtained by the other groups who conducted the same experiment showed much or less the same pattern and trend. Whenever the same pattern and trend are obtained among the other persons or groups who conducted the same experiment, therefore we can say that the results obtained are reliable. Temperature of seawater: 27oC Current velocity: 15 seconds to move 0.5 m = 0.033 ms-1
Table 7: Other group’s result
Below are the results of other group (Group B) which did the same experiment. The results obtained is much or less the same with our current result. Quadrat (0.25 m2) 1
Distance of quadrat from sea (m) 0
Population size (x 2500 if 1 cm2 quadrat was used)
Green fungus Purple fungus Brown fungus Big barnacles Small barnacles Snails Barnacles Brown fungus Green fungus Purple fungus Green fungus Purple fungus Black fungus (species Y) Brown fungus Barnacles Black fungus (species X)
Black fungus Snail Red insect Spider Black, soft body organism Black shell Sea cucumber Earthworm Table 8: Other group’s results
9 1 13 15 60 15 3 13 1 5 25 6 6 10 4 15 x 2500
36 x 2500 1 1 1 1 1 1 1
Evaluation:Experimental errors There are several errors that make our results to be inaccurate. The first error which can be occurred is when we make the line transect. The measuring tape that we used should not place on the large rock. The measuring tape should be in the straight line .This can be done by hung the measuring tape above or beside the area of investigation. The second error in this experiment happened when we need to compare the colour change of the paper indicator with the standard colour. Human error is more likely to occur. This is because normal human’s eye cannot detect the slight change of the colour. So this will affect the accuracy of the result. The third error occur when counting the number of sea grass, it is more likely to be inaccurate. This is because, sea grass is a minute species and they are very closely to each other. Plus, they are also found in large number in a small area. Thus it is impossible to count it one by one with the naked eye. This can be improved by using device such as magnifying glass. Besides that, another source of error that was found is that the camouflage effects of the organisms. As example, one might mistaken a small crab with a rock while counting the number of organisms found. The small crabs in fact have similar markings on their body that match
environments. Therefore, a thorough check should be done by having the counting process involved more than one person or the counting process should be done by the people with sharp-sightedness so that the camouflage effects of organisms can be easily spotted.
Figure 7: Fish that used camouflage technique.
Limitation There are several limitations in this experiment that cannot be avoided. The current velocity was determined during the low tide. So the current velocity is not the real velocity as we do not determined the velocity during the normal tide. The time for the orange to travel along the 2m distance is affected by the velocity of the wind. If the velocity of the wind is fast, so the time taken for the orange to travel the 2m distance is short and vice versa. The low tide also did not give all the type of species present in the area of investigation. This is because the species during the high tide may not present when low tide. So, this will affect the type and abundance of organisms there. Besides that, due to the low tide condition, some organisms were found out to be trapped in between the rocks. This was what happened where many of the sea cucumbers, small crabs and small fish in that particular area. In some cases, there were small fish and crabs trapped in small watery area on a rock and the rock itself has become the new temporary microhabitat for these organisms. Their presence will somehow disrupt the original balance of the site’s ecosystem hence affecting our result. Further investigation The experiment can be further continues by trying the line transect method in the forest instead of sea shore. Then, make the kite diagram for the organisms in the forest. After that, thorough comparison of the kite diagram for organisms at the sea shore and the forest should be made. Later, we must observe whether both of the kite diagrams show the same pattern or turn out to be different.
Conclusion:In conclusion, the distribution and abundance of a species of a specific organism at the sea shore depend on the biotic and the abiotic factor. So, the hypothesis is accepted.
Edexcel Biology for AS, Hodder Publication - C J Clegg
Edexcel Biology for AS, Pearson Publication - Fullick A
Biology ISE, Thomson Brooks/Cole - Solomon, Berg, Martin
Websites: 1. http://en.wikipedia.org/wiki/Quadrat retrieval date: 15 July 2010 2. http://geographyfieldwork.com/urban_sampling.htm retrieval date: 15 July 2010 3. http://en.wikipedia.org/wiki/Abiotic_component retrieval date: 15July 2010 4. http://en.wikipedia.org/wiki/Biotic_component retrieval date: 15July 2010 5. http://en.wikipedia.org/wiki/Aquatic_ecosystem retrieval date: 15 July 2010 6. http://en.wikipedia.org/wiki/Abundance_(ecology) retrieval date: 15 July 2010